My apologies for asking a beginners question here, but I am still having the same issues as described in this post even with the override. I'm wondering if I have not applied the override correctly as I've never used one before.

I've created a file called 'directOverride.js' which contains the override code. I see that the file is called as it is in my network trace and I have a couple of console.log() commands in there that get called.

You could simply put the override within your Ext.onReady so your browser wouldn't have to make another request.

This doesn't look like the same issue to me, though. Without the override, the request fails b/c it's sending null values to the server. With the override, it correctly sends the params with the request and all is good. The error you mention never comes into play.